Device for levelling a layer of sand

ABSTRACT

A device for levelling a sand layer (1) at the landing place of various jumping events, which device includes rails (2) on either side of the sand layer and a trolley (3) travelling back and forwards on them, which in turn includes at least a rake member (4) for loosening the sand layer, a sand-moving member (5.1, 5.2) for filling pits, and a levelling member (6) for levelling the loosened sand layer, as well as devices for moving these in a vertical direction. The sand-moving member consists of several parallel V-ploughs (5.1) pointed in the opposite direction to the levelling direction and a transverse bar (5.2) or similar together with support devices, moving after the rake member (4).

The object of the invention is a device for levelling a layer of sand asa landing place for various jumping events, which device includes railson either side of the sand layer and a trolley moving backwards andforwards along them and which further includes at least a rake memberfor loosening the sand layer, a sand-moving member for filling pits, anda levelling member for levelling the loosened sand layer, as well asdevices for moving these in a vertical direction.

During a competition the surface of the landing place is depressed afterthe jumper has left it and as a result of the footprints of themeasurers. This happens especially when the sand is damp in rainyweather. Because a jumper strikes the landing place at an angle of about45°, every change in the level of the landing place causes a differencein the length of the jumps. If the depressed surface is raised to thezero level by adding sand, then the jumper who jumps immediately afterthe raising suffers most from this. This being the case, it is ofabsolute importance when determining the correct length of a jump thatthe surface of the landing place is at the same level for each jump forthe entire duration of the competition.

One kind of sand layer levelling device is known from German patentapplication DE 2 448 830, which consists of a rake member and alevelling member. The rake member consists of pins or plate members setin two transverse rows and which extend deep into the sand layer. Therows of this kind are pulled over the sand layer, when the sand layerbecomes thoroughly loosened. After these comes a levelling member,formed by a transverse plate, which ploughs the mass over the surface tobe levelled forwards, leaving a level surface. A slightly modified sandlayer levelling device is known from Finnish patent 76395, which alsoconsists of sand moving and levelling devices attached to a trolley. Themoving member consists of a plough-like member, which can be movedlaterally at the location of a pit. The levelling member is hinged insuch a way that when it moves in the opposite direction it follows theuneven surface of the sand layer and operates only when the trolley ismoved in the levelling direction. Both of the aforementioned devices areprincipally intended for manual operation, even though in the Finnishapplication reference is made to possible mechanical operation. They arenot, however, very suitable for mechanical operation, because thetrolley can rise over uneven sand. In any event, the device inaccordance with the Finnish patent demands visual estimation of thelocation of a pit, at which the sand moving member should be set in alateral direction.

It is the intention of this invention to create an easily mechanized,efficient, and reliable sand layer levelling device. The characteristicfeatures of the invention are presented in the accompanying Patentclaims.

According to the invention it is precisely a rake member that is used,even though it demands relatively great power. In mechanical operationthis is no drawback, but by means of a rake member efficient looseningand lightening of the sand is achieved, when compaction is minimizedduring a competition.

In what follows the invention is illustrated with reference to theaccompanying Figures, which show one levelling device in accordance withthe invention.

FIG. 1 shows the levelling device seen from in front.

FIG. 2 shows the levelling device seen from the rear.

FIG. 3 shows the lifting devices of the rake and moving members seenfrom the side.

FIGS. 4 and 5 show the arrangement of the support and drive wheels ofthe trolley.

In FIGS. 1 and 2 the sand layer is marked with reference number 1, therails with reference number 2, and the trolley itself with referencenumber 3. The support wheels of the trolley run inside a C-profile rail,so that they are not able to rise, even under the greatest loading. Thefirst moving member 5.1, which is composed of several plough-likemembers, is in the front of the device and the rake member 4 is behindthe device. The plough-like members 5.1 are attached to a plate, thelower edge of which forms the levelling member 6. Bar 5.2, which formsthe second moving member, is attached by means of chains 5.21 to therake member. The spikes of the rake member 4 leave deep furrows in thesurface, so that moving member 5.2 acts as an effective pre-leveller.All the operating devices are powered by electricity, so that thetrolley includes a spring reel 12 for this purpose, which pulls thecable tight and makes possible the supply of electricity to the movingtrolley. The trolley includes a control unit 14 for controlling thevarious operations and an operating motor 13 with a transmission formoving the trolley.

The raising of the rake members and moving members is carried out withthe aid of parallelogram arms 7 and 9. These are driven by electricspindle motors 8 and 10. The spikes 4.1 and 4.2 of the rake member areattached to a beam, which in turn is attached to the frame by means ofparallelogram arms 7.1 and 7.2. The upper parallelogram arm is driven bythe aforesaid spindle motor 8. The first moving member 5.1, which iscomposed of parallel V-ploughs, is attached to plate 6.1. The lower edgeof this forms the levelling member 6 proper. The V-ploughs themselves donot at their points extend quite as far down as the levelling member 6.

The gearbox rotated by the operating motor 13 in turn drives axle 21,which rotates double chainwheels 22, FIGS. 4 and 5. These transmit thedrive through chain 16 and chainwheels 20 to axle 15, which rotatescogged belt wheel 17. Axle 15 is attached to the frame with bearings.The cogged belt 18 is located in the groove in the base of beam 2beneath the support wheels 11. Between them it is led over theaforementioned cogged belt wheel 17. Because the cogged belt 18 isattached by the ends to the ends of the rail, there is no slip andmovement of the trolley is ensured. The support wheels 11 are attachedby bearings to beam 19, which is welded to the frame of the trolley.

The levelling device is operated as follows. In FIG. 1 both the rakemember and the moving member are in the lowered position and the trolleyis moved towards the viewer. FIG. 2 shows the situation seen from theother side. The rake member 4 and the second moving member 5.2 are inoperation. When they leave the home station both are in the upperposition, but are lowered in the area of the sand layer. When thetrolley has nearly crossed the field both are raised, the moving memberfirst of all, however. In the return stage, the levelling member islowered to the desired height and then driven over the entire field,when the sand layer is levelled. Close to the rear station the levellingmember too is raised and driven to the home station.

I claim:
 1. A device for levelling a sand layer at the landing place ofvarious jumping events, the device including rails on either side of thesand layer and a trolley travelling back and forwards on the rails, thetrolley including a rake member for loosening the sand layer, asand-moving member for filling pits, and a levelling member forlevelling the loosened sand layer, as well as devices for moving saidrake, sand moving and levelling members in a vertical direction,characterized in that the sand-moving member comprises several laterallyspaced V-ploughs pointed in the opposite direction to the levellingdirection and a transverse bar together with support devices, movingafter the rake member.
 2. A device in accordance with claim 1,characterized in that the levelling member comprises a vertical platecarrying the V-ploughs, the lower edge of which levels the sand layerduring the return movement of the trolley.
 3. A device in accordancewith claim 1, characterized in that said bar behind the rake member isattached to the rake member by chains.
 4. A device in accordance withclaim 1, characterized in that the trolley includes a mechanical drivingdevice for moving it and a spring reel for leading a cable transmittingoperating power to the trolley moving backwards and forwards.
 5. Adevice in accordance with claim 1, characterized by devices for movingthe rake member in a vertical direction comprising parallelogram armsthat are hinged, and operating devices for driving the parallelogramarms.
 6. A device in accordance with claim 1, characterized in that therails are arranged to prevent the support wheels from rising even undera great loading.
 7. A device in accordance with claim 6, characterizedin that both rails include in combination two support wheels set in linenext to one another and a cogged belt located in a groove in the bottomof the rail, which is threaded over a drive wheel between these supportwheels, wherein the trolley is made moveable by rotating the drivewheel.